Note 7 - Related Party Transactions (Details Textual) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 31, 2016	Jul. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Apr. 30, 2016
Value Line Inc [Member]
Accounts Receivable, Related Parties	$ 0				$ 0		$ 0
EAM Trust [Member] | Minimum [Member]
Non Voting Revenues Interest Percent					41.00%
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement					90.00%
EAM Trust [Member] | Maximum [Member]
Non Voting Revenues Interest Percent					55.00%
EAM Trust [Member]
Assets under Management, Carrying Amount	$ 2,240,000,000		$ 2,290,000,000		$ 2,240,000,000	$ 2,290,000,000
Percentage of Assets Increased (Decreased) in Unconsolidated Entities					2.30%
Non Voting Profits Interest Percent					50.00%
NonVotingProfitsInterest, Remaining Percentage					50.00%
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement					90.00%
Percentage of Non Voting Revenues Interest in Unconsolidated Entity	49.14%	49.45%	50.16%	50.05%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable							$ 1,750,000
Percent of Revenue Interest					100.00%
Value Line Inc [Member]
Reimbursement Revenue					$ 185,000	65,000
Percentage of Non Voting Profits Interests Due from Ex Subsidiary Payable to Parent under Agreement					90.00%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	$ 1,918,000				$ 1,918,000
Percent of Revenue Interest					100.00%
Federal Income Tax Payments to Parent					$ 3,218,000	$ 1,990,000
Ownership Percentage By Parent	88.87%				88.87%